PPARalpha mRNA Research Articles

Low dose pterostilbene-mediated hepatic chemoprevention in diethylnitrosamine-treated rats: Modulation of Ppar alpha, Nrf2 and Capase3 expression

BackgroundChronic liver disease (CLD) is a leading cause for liver cancer development. Pterostilbene (PTS) is a new promising natural agent with chemo- preventive effects. We hypothesized that low dose of PTS may have a hepato-protective role. This role may result from the cross talk between peroxisome-proliferator activated receptors alpha (Ppar alpha), nuclear factor erythroid 2-related factor 2 (Nrf2) and capase3 signaling pathways. MethodsWe established diethyl nitrosamine (DENA) induced liver injury rat model then low dose of PTS was given by oral gavage for 16 weeks. We investigated serum liver function tests and hepatic levels of oxidative markers and alpha fetoprotein (AFP). Expression of Ppar alpha, Nrf2 and caspase3 by real-time quantitative polymerase chain reaction (qPCR) analysis were evaluated. Histopathological changes and immunohistochemistry for arginase-1 and glypican-3 reactivity were measured. ResultsPTS significantly improved liver function tests and hepatic oxidative stress state and decreased hepatic glypican-3 and arginase-1 expression. Moreover, PTS significantly increased Ppar alpha, Nrf2 and caspase3 expression (p < 0.01). There was significant positive correlation between Ppar alpha, Nrf2 and caspase3 mRNA expression (r = 0.8) (p < 0.01). The damage of hepatocytes architecture was hampered with PTS in DENA-treated rats.In conclusion: PTS may be a promising natural hepatoprotective agent in the DENA-induced liver injury. This effect could be mediated through the interaction between Ppar alpha, Nrf2 and caspase3.

NIACIN ALTERS THE SECRETION OF INTESTINAL LYMPHATIC HDL AND ASSOCIATED MIRNA PROFILE IN A RAT MODEL OF INSULIN RESISTANCE

Hypolipidemic effects of niacin (nicotinic acid) include lowering plasma triglycerides (TG) whilst increasing HDL-C concentration. However the mechanism of action of niacin still remains elusive. Emerging evidence shows that in addition to the liver, the intestine also contributes to whole body HDL metabolism. The effect of insulin resistance (IR) and niacin on intestinal HDL secretion is not known. Therefore the objective of this study was to determine the effect of niacin on the secretion, composition and miRNA profile of intestinal lymphatic HDL in a model of insulin resistance (IR) (JCR:LA-cp rat). IR rats were fed control chow or chow supplemented with niacin (1% w/w) for 6 weeks. The mesenteric lymph duct was cannulated and lymph sampled following an intra-gastric intralipid (fed) infusion for 6 hrs. The lymphatic HDL (1.063-1.21g/ml) fraction was separated by density ultracentrifugation; associated lipid, protein and miRNA composition was analyzed. For ex-vivo experiments, Jejunal explants from IR rats were treated with 5mg/ml niacin or nicotinamide and mRNA expression was assessed. In IR rats, apo-AI lymphatic HDL secretion was reduced (-47%) and associated with an enriched (86%) TG content, compared to non-IR rats. Interestingly, niacin was found to stimulate the secretion (number) of lymph HDL (>60%), as well as depleting the TG content compared to non-treated IR rats. Niacin (but not nicotinamide) significantly increased PPAR alpha and cpt1a mRNA, and annulled TNF alpha mRNA in jejunal explants. In lymph associated HDL from IR rats, miR223 and miR29c were both decreased compared to control. Interestingly niacin treatment increased both miR223 and miR29c in lymph associated HDL, suggesting a benefit to restore anti-inflammatory action of miR223 as well as the collagen/fibrotic repair functions of miR29c. IR may reduce the secretion of apoAI HDL into mesenteric lymph, potentially contributing to lipid enrichment and particle dysfunction. Niacin may contribute to improving CVD risk by increasing the number of lipid depleted intestinal apoAI particles. The ability of niacin to modulate miRs in the lymphatic HDL fraction may provide novel insight into hypolipidemic mechanisms of action of niacin.

Abstract 629: Niacin Beneficially Alters the Secretion of Intestinal HDL in a Rat Model of Insulin Resistance by Opposing Effects on PPAR Alpha and TNF Alpha

INTRODUCTION: Niacin is the oldest hypolipidemic drug that effectively lowers plasma triglycerides whilst increasing HDL-C concentration. However the mechanism of action of niacin still remains elusive. Emerging evidence shows that in addition to the liver, the intestine also contributes to whole body HDL metabolism. The effect of insulin resistance and niacin on intestinal HDL secretion is unclear. OBJECTIVE: To determine the effect of niacin on the secretion and composition of intestinal lymphatic HDL in a model of insulin resistance (JCR:LA-cp rat). METHODS: Insulin resistant (IR) rats were fed control chow or chow supplemented with niacin (1% w/w) for 6 weeks. The mesenteric lymph duct was cannulated and lymph sampled following an intra-gastric intralipid (fed) infusion for 6 hrs. The lymphatic HDL (1.063-1.21g/ml) fraction was separated by density ultracentrifugation; associated lipid and protein composition was analyzed. Primary enterocytes were isolated by an adaptation of the Wieser method. Jejunal explants from IR rats were treated with 5mg/ml niacin or nicotinamide and mRNA expression was assessed. RESULTS: In IR rats, apo-AI lymphatic HDL secretion was reduced (-47%), but associated TG content enriched (86%), compared to non-IR rats. Interestingly, niacin was found to stimulate the secretion of lymph HDL (&gt;60%) compared to non-treated IR rats. Niacin treatment also normalized the TG content of lymphatic HDL particles. In parallel experiments, niacin was also shown to beneficially reduce lymphatic apoB secretion, suggesting concomitant pathways. Primary enterocytes isolated from niacin treated animals had increased ABCA1 and PPAR alpha mRNA compared to untreated control. Further, niacin (but not nicotinamide) significantly increased PPAR alpha and CPT1a mRNA, while annulling TNF alpha mRNA in treated jejunal explants. Conversely, there was no effect of niacin or nicotinamide treatment on ATGL, PLIN2 or ATG5. CONCLUSION: Insulin resistance may reduce the secretion of apoAI HDL into mesenteric lymph, potentially contributing to particle dysfunction. Niacin may contribute to improving CVD risk by restoring the number and TG enrichment of intestinal apoAI particles.

Telmisartan increases lipoprotein lipase expression via peroxisome proliferator-activated receptor-alpha in HepG2 cells

In addition to their hypotensive properties, angiotensin receptor blockers (ARBs) have been shown to exert clinical antidyslipidemic effects. The mechanism underlying these ARB lipid metabolic effects remains unclear. Some ARBs, for example, telmisartan, activate peroxisome proliferator-activated activated receptor-gamma (PPAR-gamma). We hypothesized that PPAR-gamma–activating ARBs might exert antidyslipidemic effects via PPAR-alpha. In this study, we assessed the effect of telmisartan on the expression of PPAR-alpha and lipoprotein lipase (LPL). PPAR-alpha expression was detected by reverse-transcription polymerase chain reaction and Western blot in HepG2 hepatocytes as well as differentiated C2C12 myocytes treated with increasing concentrations of telmisartan (0.1–10 μmol/L) for 48 h. Results showed that 1 μmol/L and 10 μmol/L telmisartan significantly increased the expression of PPAR-alpha mRNA and protein in HepG2 cells (p < 0.01). No effect was shown in differentiated C2C12 cells. Similarly, 1 µmol/L and 10 μmol/L telmisartan significantly increased the expression of LPL mRNA and protein in HepG2 cells (p < 0.01), and this increase was significantly (p < 0.01) inhibited by the PPAR-alpha–specific antagonist MK886. These results indicate that certain of the antidyslipidemic effects of telmisartan might be mediated via increased PPAR-alpha–dependent induction of LPL expression.

The role of microRNA-9 in hepatocellular oncogenesis.

168 Background: Hepatocellular carcinoma (HCC) is the main type of liver cancer. MicroRNAs are non-coding RNAs that have been involved in the pathogenesis of different cancer types. Our aim was to identify microRNAs that have functional and clinical significance in liver oncogenesis and understand how manipulation of their levels could have a therapeutic potential. Methods: MicroRNA expression analysis was performed in 38 HCC tissues and 25 normal liver tissues. A microRNA library (318 microRNAs) was transfected in SNU-449 liver cancer cells and invasiveness was measured 24 h later by a matrigel invasion assay. Cell growth and matrigel invasion assays were performed in SNU-449 cells that were transfected with miR-9 or antisense-miR-9 (20nM). TargetScan algorithm was used to identify miR-9 direct downstream target genes. The mRNA levels of PPARalpha, and E-cadherin were assessed by real-time PCR 48h after miR-9 overexpression and down-regulation in SNU-449 cells. Results: MicroRNA expression analysis in 38 HCCs and 25 normal liver tissues identified a 25-microRNA signature of HCC. Integration of the library screen and patient data revealed that miR-9 has clinical and functional relevance for liver cancer. Specifically, we found that miR-9 increases 2.7-fold the invasiveness and the growth of SNU-449 cells, 48h post transfection. Bioinformatic analysis revealed that miR-9 has a binding site in the 3’UTR of PPARalpha gene. MiR-9 overexpression inhibited 35% PPARalpha 3’UTR luciferase activity and 60% mRNA levels, while miR-9 down-regulation led to 75% increased PPARalpha mRNA levels. These data suggest that miR-9 targets directly the 3'UTR of PPARalpha and regulates its expression levels in liver cancer cells. In addition, miR-9 overexpression led to 95% suppression of E-cadherin mRNA levels in SNU-449 cells, thus increasing their metastatic potential. Conclusions: We found that miR-9 is highly overexpressed in liver cancer patients and its up-regulation increases the growth and metastatic potential of liver cancer cells. Overall these data suggest that miR-9 is a novel oncogene involved in liver oncogenesis and its suppression could have therapeutic potential in liver cancer patients.

Expression of FXR mRNA, PPAR alpha mRNA and bile acid metabolism related genes in intrahepatic cholestasis of pregnant rats

To study the expressions of FXR, PPARa and Bile acid metabolism related genes in intrahepatic cholestasis of pregnant rats. 60 clean SD pregnant rats were selected and divided randomly into three groups. Since the 13th day of pregnancy rats in control group were injected subcutaneously with refined vegetable oil 2.0 mg/kg/d Rats in no-treated group were injected subcutaneously with the 17-a-ethynylestradiol (EE) 1.25 mg/kg/d until the 17th day. Those rat ih treated group were injected subcutaneously with the 17-a-ethynylestradiol (EE) 1.25 mg/kg/d until the 17th day and then were treated with fenofibrate for another four days until the 21th day. All rats were killed at the 21th day and livers were collected for study. The levels of serum TBA were examined by ELISA. The mRNA expressions of PPARa, FXR, CYP7A1, CYP27A1 and CYP8B1 were examined by real-time PCR. (1) The levels of TBA were significantly higher in no-treated group (68.7+/-4.2)mumol/L and treated group (69.5+/-3.8)mumol/L compared with that of control group (26.6+/-2.3)mumol/L at the 17th day (P value is less than 0.05) and no difference found between treated and no-treated groups (P value is more than 0.05). The levels of TBA were higher in no-treated group (69.4+/-3.7)mumol/L and treated group (48.5+/-4.8)mumol/L as compared to control group (27.1+/-3.2)mumol/L at the 21th day (P value is less than 0.05). The lever of TBA was significantly lower in Treated group compared with No-treated group (P value is less than 0.05). (2) The mRNA expressions of CYP7A1, FXR, CYP27A1 and CYP8B1 increased in No-treated group (1.55+/-0.03, 1.75+/-0.02, 2.45+/-0.01, 2.15+/-0.01, respectively) and were all higher as compared to control group (0.75+/-0.02, 1.25+/-0.03, 0.65+/-0.03, 1.50+/-0.02, respectively) (P value is less than 0.05). However, the mRNA expression of PPARa decreased in No-treated group (0.85+/-0.02) compared with control group (1.45+/-0.02) (P value is less than 0.05). The mRNA expressions of CYP27A1, PPARa and CYP8B1 increased in treated group (1.25+/-0.01, 1.65+/-0.05, 1.65+/-0.02, respectively) and were all higher than that of control group (P value is less than 0.05). Abnormal expressions of CYP7A1, FXR, CYP27A1, CYP8B1 and PPARa may play a role in pathogenesis of estrogen-induced intrahepatic cholestasis. Activator of PPARa may be used as therapeutical drug for ICP.

Oxidative stress and inflammation modulate peroxisome proliferator‐activated receptors with regional discrepancy in diabetic heart

Peroxisome proliferator-activated receptors (PPARs) play a pivotal role in myocardial lipid and glucose homeostasis. We investigated the effects of diabetes on PPAR isoforms in different cardiac regions and explored whether proinflammatory cytokines or oxidative stress modulate PPARs in diabetic hearts. Male Wistar rats were separated into control, diabetes and ascorbate-treated diabetes groups. Real-time PCR and Western blot analysis were performed on PPAR isoforms, tumour necrosis factor (TNF)-alpha and interleukin (IL)-6, from left and right atria and ventricles. Nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidase activity was quantified through photometric measurements. In control hearts, PPAR-alpha was most expressed, and PPAR-gamma least expressed in mRNA and protein levels. Diabetes decreased the protein and mRNA levels of PPAR-alpha and PPAR-delta. Ascorbate attenuated the diabetes-induced down-regulations of PPAR-alpha and PPAR-delta proteins in all cardiac regions and down-regulation of PPAR-alpha mRNA in the left atrium. In PPAR-gamma, the protein and mRNA levels were increased in diabetic atria and ventricles, which were decreased by ascorbate. Moreover, diabetes increased the TNF-alpha and IL-6 protein levels, and NAD(P)H oxidase activities in atria and ventricles. Ascorbate attenuated the increase of TNF-alpha, IL-6 protein levels and NAD(P)H oxidase activity in the atria, but only attenuated the increase of NAD(P)H oxidase activities in the ventricles. Peroxisome proliferator-activated receptor isoforms are differentially expressed in the atria and ventricles. Diabetes can modulate PPARs through increased inflammatory cytokines and oxidative stress, which are attenuated by ascorbate treatment.

Potential Effects of Chrysin on MDA-MB-231 Cells

This study aims to elucidate the effects of chrysin on human ER-negative breast cancer cell line, MDA-MB-231. The study demonstrated that treatment of MDA-MB-231 cells with 20 μM chysin for 48 h significantly inhibited the growth of MDA-MB-231 cells and induced cytoplasmic lipid accumulation in the cells, but that the observed of cell death was not caused by apoptosis. The expression of PPARalpha mRNA in chrysin-treated MDA-MB-231 cells was significantly increased, which was likely associated to the proliferation of the cells post chrysin treatment.

Fasting promotes the expression of SIRT1, an NAD+-dependent protein deacetylase, via activation of PPARα in mice

Calorie restriction (CR) extends lifespans in a wide variety of species. CR induces an increase in the NAD(+)/NADH ratio in cells and results in activation of SIRT1, an NAD(+)-dependent protein deacetylase that is thought to be a metabolic master switch linked to the modulation of lifespans. CR also affects the expression of peroxisome proliferator-activated receptors (PPARs). The three subtypes, PPARalpha, PPARgamma, and PPARbeta/delta, are expressed in multiple organs. They regulate different physiological functions such as energy metabolism, insulin action and inflammation, and apparently act as important regulators of longevity and aging. SIRT1 has been reported to repress the PPARgamma by docking with its co-factors and to promote fat mobilization. However, the correlation between SIRT1 and other PPARs is not fully understood. CR initially induces a fasting-like response. In this study, we investigated how SIRT1 and PPARalpha correlate in the fasting-induced anti-aging pathways. A 24-h fasting in mice increased mRNA and protein expression of both SIRT1 and PPARalpha in the livers, where the NAD(+) levels increased with increasing nicotinamide phosphoribosyltransferase (NAMPT) activity in the NAD(+) salvage pathway. Treatment of Hepa1-6 cells in a low glucose medium conditions with NAD(+) or NADH showed that the mRNA expression of both SIRT1 and PPARalpha can be enhanced by addition of NAD(+), and decreased by increasing NADH levels. The cell experiments using SIRT1 antagonists and a PPARalpha agonist suggested that PPARalpha is a key molecule located upstream from SIRT1, and has a role in regulating SIRT1 gene expression in fasting-induced anti-aging pathways.

Two weekly sessions of combined aerobic and resistance exercise are sufficient to provide beneficial effects in subjects with Type 2 diabetes mellitus and metabolic syndrome

This study was performed to establish whether only 2 sessions per week of combined aerobic and resistance exercise are enough to reduce glycated hemoglobin (HbA(1c)) and to induce changes in skeletal muscle gene expression in Type 2 diabetes mellitus (DM2) subjects with metabolic syndrome. Eight DM2 subjects underwent a 1-yr exercise program consisting of 2 weekly sessions of 140 min that combined aerobic [at 55-70% of maximal oxygen uptake (VO(2max))] and resistance circuit training [at 60-80% of 1 repetition maximum (RM)]. The training significantly improved VO(2max) (from 33.5+/-3.8 ml/kg/min to 38.2+/-3.5 ml/kg/min, p=0.0085) and muscle strength (p<0.05). Changes over baseline were significant for HbA(1c), reduced by 0.45% (p=0.0084), fasting blood glucose (from 8.8+/-1.5 to 6.9+/-2.2 mmol/l, p=0.0132), waist circumference (from 98.9+/-4.8 to 95.9+/-4.6 cm, p=0.0054), body weight (from 87.5+/-10.7 to 85.7+/-10.1 kg, p=0.0375), systolic blood pressure (from 137+/-15 to 126+/-8 mmHg, p=0.0455), total cholesterol (from 220+/-24 to 184+/-13 mg/dl, p=0.0057), and LDL-cholesterol (from 150+/-16 to 105+/-15 mg/dl, p=0.0004). Mitochondrial DNA/nuclear DNA ratio at 6 and 12 months did not change. There was a significant increase of mRNA of peroxisome proliferator- activated receptor (PPAR)-gamma after 6 months of train - ing (p=0.024); PPARalpha mRNA levels were significantly increased at 6 (p=0.035) and 12 months (p=0.044). The mRNA quantification of other genes measured [mitochondrially encoded cytochrome c oxidase subunit II (MTCO2), cytochrome c oxidase subunit Vb (COX5b), PPARgamma coactivator 1alpha (PGC- 1alpha), glucose transporter 4 (GLUT 4), forkhead transcription factor BOX O1 (FOXO-1), carnitine palmitoyltransferase 1 (CPT-1), lipoprotein lipase (LPL), and insulin receptor substrate 1 (IRS-1)] did not show significant changes at 6 and 12 months. This study suggests that a twice-per-week frequency of exercise is sufficient to improve glucose control and the expression of skeletal muscle PPARgamma and PPARalpha in DM2 subjects with metabolic syndrome.

Antihyperglycemic and antihyperlipidemic action of Cinnamomi Cassiae (Cinnamon bark) extract in C57BL/Ks db/db mice

In previous study, the anti-diabetic effect of Cinnamomi Cassiae extract (Cinnamon bark: Lauraceae) in a type II diabetic animal model (C57BIKsj db/db) has been reported. To explore their mechanism of action, in present study, the effect of cinnamon extract on anti-hyperglycemia and anti-hyperlipidemia was evaluated by measuring the blood glucose levels, serum insulin, and adiponectin levels, serum and hepatic lipids, PPARalpha mRNA expression in liver and PPARgamma mRNA expression in adipose tissue, respectively. Male C57BIKs db/db mice were divided into a diabetic group and cinnamon extract treated group and examined for a period of 12 weeks (200 mg/kg, p.o). The fasting blood glucose and postprandial 2 h blood glucose levels in the cinnamon treated group were significantly lower than those in the control group (p < 0.01), whereas the serum insulin and adiponectin levels were significantly higher in the cinnamon treated group than in the control group (p < 0.05). The serum lipids and hepatic lipids were improved in the cinnamon administered group. Also the PPARalpha mRNA (liver) and PPARgamma mRNA (adipose tissue) expression levels were increased significantly in the cinnamon treated group (p < 0.05). Our results suggest that cinnamon extract significantly increases insulin sensitivity, reduces serum, and hepatic lipids, and improves hyperglycemia and hyperlipidemia possibly by regulating the PPAR-medicated glucose and lipid metabolism.

Liver nuclear hormone receptor PPAR, LXR and RXR expression and blood lipid and glucose levels in susceptible and resistent to hepatocarcinogenesis strain of mice

Earlier it was shown that male mice of the DD/He strain were highly susceptible to ortho-aminoasotoluene (OAT) induced hepatocarcinogenesis, and resistant to spontaneous liver tumor development as compared to the CC57BR/Mv strain. In the present work we have made a comparative investigation of peroxisome proliferator-activated receptor (PPAR), liver X-receptor (LXR) and retinoic X-receptor (RXR) mRNA levels in liver as well as concentrations of corticosterone, glucose, lipids and insulin in blood of male DD/He and CC57BR/Mv mice. Using the multiplex RT-PCR method it was found that PPAR-alpha, PPAR-gamma, RXR-alpha and RXR-beta mRNA content was essentially decreased in the liver of DD mice as compared to mice of the CC57BR strain. No significant interstrain differences of LXR-alpha and LXR-beta mRNA content were found. In DD micetere was more then the 3-fold decrease of blood content of corticosterone, which is involved in PPAR and RXR regulation. DD mice demonstrated a significant decrease in blood serum glucose and insulin concentrations as well as higher reactivity to insulin as compared with CC57BR mice. Elevated blood total cholesterol and cholesterol HDL level were found in DD mice whereas triglyceride content was basically the same in both mouse strains. It is known that glucocorticoids, PPAR and RXR play crucial role in transcription regulation of inflammation response. Therefore our data allow to suggest that decreased corticosterone level in blood, PPAR and RXR mRNA content in liver of the DD strain may lead to induction of inflammation by OAT exposure, resulting in a high incidence of tumorigenesis in this strain.

Effect of peroxisome proliferator-activated receptor-α siRNA on hypertension and renal injury in the rat following nitric oxide withdrawal and high salt diet

Peroxisome proliferator-activated receptor (PPAR)-alpha has been implicated in the regulation of normal and pathological cellular functions, but the effect of specific gene silencing on PPARalpha-mediated function is not fully defined. This study evaluated the role of PPARalpha in hypertensive renal injury induced by nitric oxide withdrawal and high salt (4% NaCl) diet [high salt/N(omega)-nitro-L-arginine (L-NNA)]. Three PPARalpha siRNA clones, siRNA(790-811), siRNA(974-995) or siRNA(1410-1431), directed at the DNA or ligand binding domain of PPARalpha mRNA or scrambled siRNA was cloned into plasmid expression vector and was injected (10 microg intravenously) in hypertensive rats. Twenty-four-hour readings of blood pressure and heart rate were taken in conscious rats using radiotelemetry. Kidney injury was evaluated by determining N-acetyl-beta-glucosaminidase excretion, expression of kidney injury molecule-1 and histopathology. PPARalpha mRNA and protein expression were also determined. High salt/L-NNA increased PPARalpha mRNA expression three-fold, and this was abolished in rats treated with PPARalpha siRNA(790-811), siRNA(974-995) or siRNA(1410-1431). High salt/L-NNA also increased blood pressure but reduced heart rate without affecting pulse pressure. However, blood pressure was further increased in rats treated with PPARalpha siRNA(790-811) (37 +/- 3%, P < 0.05). High salt/L-NNA also increased N-acetyl-beta-glucosaminidase excretion and expression of kidney injury molecule-1. However, PPARalpha siRNA(790-811) did not affect N-acetyl-beta-glucosaminidase excretion but reduced kidney injury molecule-1 expression. Histopathology of kidney tissues in high salt/L-NNA-treated rats revealed global, fibrinoid and tubular interstitial necrosis that was blunted by PPARalpha siRNA(790-811). These data suggest that increased PPARalpha expression is a protective mechanism in hypertensive renal injury induced by nitric oxide withdrawal/high salt diet and that siRNAs targeting the DNA-binding domain of PPARalpha gene elicited differential effects on hypertension and kidney injury.

Counter-regulation by atorvastatin of gene modulations induced by L-NAME hypertension is associated with vascular protection

Statins, 3-hydroxyl-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, protect against deleterious effects of chronic nitric oxide inhibition. We aimed at determining the genes and pathways involved in the protective effect of statin treatment during hypertension. Chronic inhibition of nitric oxide synthesis by Nω-nitro- l-arginine methyl ester (L-NAME) induced accelerated hypertension which was slightly reduced by cotreatment with atorvastatin (100 mg/kg/day). Gene expression profile of aortic media was strongly modified by atorvastatin cotreatment which prevented modulation of many genes regulated by L-NAME administration (described in Dupuis, M., Soubrier, F., Brocheriou, I., Raoux, S., Haloui, M., Louedec, L., Michel, J.B., Nadaud, S., 2004. Profiling of aortic smooth muscle cell gene expression in response to chronic inhibition of nitric oxide synthase in rats. Circulation 110, 867–873). The functional classification of these genes highlighted several major biological pathways modulated in aortic media by atorvastatin: effectors involved in smooth muscle tone; extracellular matrix; intracellular mediators of cell proliferation. Moreover, atorvastatin partially prevented arterial wall thickening, TGF-β pathway activation, MCP-1 induction and smooth muscle cell proliferation induced by L-NAME treatment although blood pressure was only slightly reduced, suggesting mechanisms independent of blood pressure levels. The induction of PPARalpha mRNA expression by atorvastatin in L-NAME treated rats also suggests that this pathway could participate in the protective effect. In conclusion, our data show that atorvastatin specifically antagonizes a set of genes modulated by L-NAME-induced accelerated hypertension.

Influence of flavonoid-rich fraction from Spermacoce hispida seed on PPAR-alpha gene expression, antioxidant redox status, protein metabolism and marker enzymes in high-fat-diet fed STZ diabetic rats

We investigated the influence of the flavonoid-rich fraction from Spermacoce hispida seed (S-Frf) on PPAR-alpha gene expression, plasma and erythrocyte antioxidants status, protein metabolism, and marker enzymes in diabetic hyperlipidemic rats. Hyperlipidemia was induced by feeding a 20% high fat diet (HFD) to male albino Wistar rats for 66 days. Diabetes was induced on the 17th day by a single i.p. injection of streptozotocin (50 mg/kg). When compared with diabetic hyperlipid-emic rats, plasma TBARS and LOOH levels decreased, the activities of enzymic antioxidants (SOD, CAT, GPx) and plasma GSH levels increased in the S-Frf fed group. The activities of plasma hepatic markers serum aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase, and levels of plasma urea, uric acid, creatinine, globulin, A/G ratio significantly decreased, whereas liver weight, total protein, and albumin increased. Oral administration of S-Frf up-regulates PPAR-alpha (peroxisome proliferator activated receptor alpha) gene expression, activates fatty acid catabolism, and is involved in the control of lipoprotein assembly in liver. The results show that S-Frf has an antihyperlipidemic effect, improves antioxidant status, and alleviates liver and kidney damage associated with HFD-fed-STZ rats by up-regulating PPAR-alpha mRNA.

Body weight loss in beef cows: I. The effect of increased β-oxidation on messenger ribonucleic acid levels of uncoupling proteins two and three and peroxisome proliferator-activated receptor in skeletal muscle

Twenty-six Angus-cross cows were studied during BW loss (WL) and BW maintenance (WM) to examine the effects of elevated beta-oxidation on mRNA levels of NEFA-responsive signaling molecules in skeletal muscle. At the end of the WL and WM sampling periods, muscle biopsies were removed from the biceps femoris and mRNA levels were measured using real-time PCR. In comparison with WM, cows undergoing WL had elevated mRNA levels of carnitine palmitoyltransferase 1 (4.6-fold), fatty acid binding protein 3 (2.0-fold), and acyl-coenzyme A oxidase 1 (2.8-fold), all of which are indicators of beta-oxidation. Levels of mRNA of the NEFA-responsive signaling molecules PPAR alpha, delta, and gamma increased 2.0-fold, 2.2-fold, and 1.84-fold, respectively, during WL. Uncoupling proteins 2 and 3 also had increased mRNA (3.0-fold and 6.0-fold, respectively) during WL, but Western blot analysis found no changes in protein abundance of uncoupling protein 3. Uncoupling protein expression can be directly stimulated by elevated NEFA, potentially to protect cells from damage by lipid oxidation by-products. Thus, an increase in mRNA levels of genes involved in beta-oxidation of fatty acids and fatty acid by-products occurs during BW loss in beef cattle. These data support previous findings in nonruminants and suggest that these genes play a role in the same physiological processes in ruminants.

Deletion of angiotensin II type I receptor reduces hepatic steatosis

A distinct subgroup of angiotensin II type 1 receptor (AT1R) blockers (ARBs) have been reported to suppress the development of hepatic steatosis. These effects were generally explained by selective peroxisome proliferator-activated receptor (PPAR) gamma modulating properties of ARBs, independent of their AT1R blocking actions. Here, we provide genetic evidence of the direct role for AT1R in hepatic steatosis. The effect of AT1R deletion on steatohepatitis was investigated in AT1a(-/-) mice. Furthermore, the influence of AT1R inhibition by telmisartan as well as gene silencing of AT1R by siRNA was assessed in an in vitro experiment using HepG2 cells. Compared to wild-type (WT), AT1a(-/-) mice fed methionine-choline deficient (MCD) diet resulted in negligible lipid accumulation in the liver with marked induction of PPARalpha mRNA. In vitro experiments also demonstrated reduced cellular lipid accumulation by telmisartan and AT1R knockdown following exposure of long chain fatty acids. This is presumably explained by the observation that the expression of PPARalpha and its target genes were significantly up-regulated in specific siRNA treated HepG2 cells. Our data indicate, in addition to pharmacological effect of ARBs on PPARgamma activation, a key biological role for AT1R in the regulation of hepatic lipid metabolism.

Altered Expression of Nuclear Receptors Affects the Expression of Metabolic Enzymes and Transporters in a Rat Model of Cholestasis

Hepatic metabolism is altered in some clinical conditions owing to the changes in the expression of metabolic enzymes and transporters. Therefore, we think that investigating the altered expression of metabolic enzymes and transporters is of particular significance to studies on drug disposition in some clinical conditions. We also believe that a simultaneous in vivo investigation of all factors affecting nuclear receptors and regulated genes is important to understand the relationship between nuclear receptors and their target genes. In this study, we induced cholestasis in rats by bile duct ligation (BDL), and investigated the changes in the mRNA expression of metabolic enzymes, transporters, and nuclear receptors and the protein levels of nuclear receptors in the nucleus by reverse transcriptase-polymerase chain reaction and Western blotting. In the liver of the rats subjected to BDL, the mRNA expression levels of cytochrome P450, conjugation enzymes, and transporters were concomitantly altered. The altered mRNA and protein levels of constitutive androstane receptor (CAR) and peroxisome proliferator-activated receptor alpha (PPARalpha) in the nucleus were consistent with the changes in the plasma concentrations of total and conjugated bilirubin and fatty acid, respectively. The mRNA expression of CAR and PPARalpha was linearly associated with the expression of the corresponding target genes. These results suggested that the increase in the levels of bilirubin and fatty acid on the BDL groups altered the mRNA and protein levels of CAR and PPARalpha, respectively in the nucleus, and this in turn altered the mRNA expression of metabolic enzymes and transporters as a hepatoprotective mechanism.

Regulation of hepatic peroxisome proliferator‐activated receptor α expression but not adiponectin by dietary protein in finishing pigs

Soy protein regulates adiponectin and peroxisome proliferator-activated receptor alpha (PPARalpha) in some species, but the effect of dietary soy protein on adiponectin and PPARalpha in the pig has not been studied. Therefore, the objective of this study was to determine whether soya bean meal reduction or replacement influences serum adiponectin, adiponectin mRNA, serum metabolites and the expression of PPARalpha and other genes involved in lipid deposition. Thirty-three pigs (11 pigs per treatment) were subjected to one of three dietary treatments: (i) reduced crude protein (CP) diet containing soya bean meal (RCP-Soy), (ii) high CP diet containing soya bean meal (HCP-Soy) or (iii) high CP diet with corn gluten meal replacing soya bean meal (HCP-CGM) for 35 days. Dietary treatment had no effect on overall growth performance, feed intake or measures of body composition. There was no effect of dietary treatment on serum adiponectin or leptin. Dietary treatment did not affect the abundance of the mRNAs for adiponectin, PPARalpha, PPARgamma2, lipoprotein lipase or fatty acid synthase in adipose tissue. The mRNA expression of PPARalpha, PPARgamma2, lipoprotein lipase or fatty acid synthetase in loin muscle was not affected by dietary treatment. In liver tissue, the relative abundance of PPARalpha mRNA was greater (p < 0.05) in pigs fed the HCP-Soy diets when compared to pigs fed RCP-Soy or HCP-CGM diets. Hepatic mRNA expression of acyl-CoA oxidase or fatty acid synthase was not affected by dietary treatment. Western blot analysis indicated that hepatic PPARalpha protein levels were decreased (p < 0.05) in pigs fed the RCP-Soy diets when compared to pigs fed the HCP-Soy diets. These data suggest that increasing the soy protein content of swine diets increases hepatic expression of PPARalpha without associated changes in body composition.

Potential Relationship between Hepatobiliary Osteopontin and Peroxisome Proliferator–Activated Receptor α Expression following Ethanol-Associated Hepatic Injury In Vivo and In Vitro

Osteopontin (OPN) up-regulation is known to mediate hepatic inflammation in a rodent model of alcoholic liver disease (ALD) and alcohol ingestion is reported to inhibit hepatic peroxisome proliferator-activated receptor-alpha (PPAR-alpha) activity leading to hepatic steatosis and inflammation. Therefore, the objective of this study was to investigate the potential relationship between the anti-inflammatory PPAR-alpha and proinflammatory OPN in rats and mice livers, and cell cultures of hepatocytes and biliary epithelium. Experiments were designed to evaluate the influence of ethanol (EtOH), lipopolysaccharide (LPS), and acetaldehyde (ACA) on OPN and PPAR-alpha expression levels in vivo (rats and mice) and in vitro (hepatocytes and biliary epithelium). Adult Sprague-Dawley rats and C57BL6 mice were fed EtOH-containing Lieber-DeCarli liquid diet for 6 weeks and injected with a single dose of LPS. A combination of EtOH and LPS treated rats and mice showed significant induction of hepatic OPN expression compared with the controls. Similarly, cells exposed to physiological doses of EtOH, LPS, a combination of EtOH and LPS, and ACA resulted in increased OPN protein and mRNA expression. Rats and mice in ALD model and cells treated with EtOH and ACA showed downregulation of PPAR-alpha mRNA. Also, DNA binding activity of PPAR-alpha to PPAR response element was significantly reduced following treatment. Overexpression of PPAR-alpha rescued the reduced PPAR-alpha activity and PPAR-alpha agonist, bezafibrate, elevated PPAR-alpha activity after treatment of EtOH, LPS, and ACA when cells were exposed by bezafibrate. To further delineate the potential relationship between OPN and PPAR-alpha, OPN(-/-) mice showed no change of PPAR-alpha mRNA level although wild-type mice showed downregulation of PPAR-alpha mRNA after EtOH treatment. In conclusion, the current study suggests that OPN is induced by EtOH and its metabolite ACA and opposite relationship likely exist between PPAR-alpha and OPN expression within the liver during ALD.